The invention relates to a novel fuse and a metallic element for that fuse. The fuse can be used in fuseholders having either male or female terminal receiving clips.
Conventional blade fuses are well-known in the art. The modern electrical blade fuse was perfected by Littelfuse, Inc., the assignee of the present invention, and was described in many patents by the assignee. These patents include, but are not limited to, Littelfuse""s U.S. Pat. Nos. 3,909,767; 4,023,265; 4,131,869; 4,580,124; 4,604,602; 4,635,023; 4,661,793; 4,997,393; 5,139,443; 5,663,861; and 5,668,521.
Some of fuses described in these patents include either a V-shaped or a sinusoidal-shaped fuse link. One example of such a V-shaped fuse link is that shown in U.S. Pat. No. 4,131,869. The V-shaped fuse link is shown as item 20 in FIG. 13 of the ""869 patent, and is described at column 6, line 56, through column 7, line 18 of the ""869 patent.
As is well-known in the art, blade fuses of the types shown in the above-referenced patents protect electrical circuits from anomalies such as current overloads. This protection results, for example, from the creation of a short in the fuse, and therefore in the circuit protected by the fuse, upon certain current overload conditions. Particularly, the fuse link breaks or opens upon current overload over a predetermined length of time.
Currently, blade fuses include male type terminals. Such male type terminals are shown as item 16 in FIG. 1 of U.S. Pat. No. 4,560,227 (xe2x80x9cthe ""227 patent), which is assigned to the assignee of the present invention. These male-type terminals are inserted into the corresponding female terminal-receiving clips 24 of a fuseholder unit 10, as shown in FIGS. 1 and 2A of the ""227 patent.
The blade fuses shown in the ""227 patent have been satisfactorily used throughout the world for nearly thirty years. There is, however, a desire to overcome certain design deficiencies of fuseholders having such female terminal-receiving clips.
First, these female terminal-receiving clips include moving parts. For example, the receiving clips have parallel planar elements that are closely spaced apart from each other. The spacing of these planar elements is less than the thickness of the male terminals which the elements receive. Thus, when the male terminals enter the receiving clips, the parallel planar elements, which are biased towards each other by spring-like components, move outwardly away from each other. This structure ensures that the receiving clips tightly and securely grip the male terminals. However, like all structures with moving parts, this structure is also subject to wear. In particular, the springs which bias the planar elements can lose their resiliency, and thus their effectiveness in biasing the planar elements toward each other. If this happens, the two inadequately biased receiving clips may be incapable of securely holding the male terminals. This in turn compromises the electrical contact between the two receiving clips and the male terminal received by those clips.
Second, the structure of female terminal receiving clips makes them inherently more susceptible to damage from electrical problems arising in the circuits which their fuses protect. When severe damage occurs, it is necessary to either replace the receiving clips or replace the fuseholder. Because most fuseholders do not provide for easy removal of the female terminal receiving clips, the first of these two options is difficult, and requires the employment of skilled technicians. Because fuseholders are costly and because their replacement generally also requires the employment of a technician, the second option is relatively expensive.
There are certain types of fuses, other than blade fuses, that have female terminals. Examples are those fuses shown in U.S. Pat. Nos. 5,581,225, 4,570,147; 4,751,490; 4,869,972; and 4,871,990. Such fuses, however, are somewhat complex in structure, and thus somewhat expensive to manufacture.
In addition, these fuses are not blade fuses, and are not useful in fuseholders with female terminal receiving clips.
It would be advantageous to design a fuse that avoids these deficiencies and problems.
The invention is a metallic element for a fuse, and a blade fuse that includes that metallic element. Like typical blade fuses, this blade fuse may be mounted in a fuseholder. Unlike typical blade fuses, this fuse may be mounted in a fuseholder having either male terminal receiving clips or female terminal receiving clips.
The metallic element includes two terminal portions, also simply known as terminals. Each of these terminal portions are made of a first prong and a second prong. In fact, as will be seen in the accompanying FIGURES, two of the three portions of the preferred embodiment of the metallic element of the invention look somewhat like a tuning fork. As with a tuning fork, the second prong is spaced apart from the first prong. Completing the metallic element is a fusible link that is secured to each of the two terminal portions.
In the metallic element of the invention, a gap is formed between the spaced apart first and second prongs. This gap is shaped and sized in a manner that will ensure secure engagement of the first and second prongs with male terminal blade-receiving clips.
The metallic element of the invention is formed in a manner that results in a fuse that is a dual use fuse. What this means is that the resulting fuse can be used with fuseholders having either male or female terminal receiving clips. When inserted into a fuseholder having a female terminal receiving clip, the first and second prongs of each of the terminal portions cooperatively fit into a corresponding female terminal receiving clip. In contrast, when inserted into a fuseholder having a male terminal receiving clip, the gap between the first and second prongs of each of the terminal portions of the metallic element tightly engage the male terminal receiving clip of the fuseholder.
Preferably, to provide adequate strength, the terminal portions of the metallic element are made of a copper alloy. It is also preferable that the metallic element is made up of three separate pieces, i.e., the two terminals and the fusible link. There are many advantages to the present invention. First, as suggested above, the construction of the invention allows it to be used with fuseblocks having either male or female terminal receiving clips.
Second, when the invention is used with fuseblocks having male terminal receiving clips, the female portion of the novel blade fuse terminal is used. In this way, if the female terminal is damaged due to electrical problems in the circuit being protected by the fuse, the replacement of the female terminal can be simply accommodated by replacement of the blade fuse, rather than by replacement of the terminal receiving clips.
Third, although there are several different types of fuses with female terminals, including the fuses described in U.S. Pat. Nos. 5,581,225, 4,570,147; 4,751,490; 4,869,972; and 4,871,990, their construction is much more complex and costly than the construction of the fuse of the present invention. Fourth, unlike the present invention, these prior art fuses with female terminals are not dual use fuses, i.e., they are not adaptable for use with fuseholders having both male and female terminal receiving clips.